Industrial robot

ABSTRACT

A dust-free industrial robot of high performance includes an internal air space substantially closed by arms, articulation members, bearings or covers or a combination thereof in a manner to separate the rotating, sliding and contacting portions of structural elements such as the arms, articulation members, bearings and a drive source from the outside air. The air pressure in the internal air space is made lower than that of the outside air to prevent dust produced during the operation of the robot from being scattered to the outside air.

TECHNICAL FIELD

The present invention relates to an industrial robot adapted for use infactories which have to be kept away from dust, such as factories formanufacturing semiconductors, optical parts and other precise parts.

BACKGROUND OF THE INVENTION

In general, an industrial robot has many dust generating parts such asbearings of articulates, brushes of servomotors and so forth. When suchan industrial robot is used in a factory where air has to be keptextremely clean, it is necessary to take a suitable measure forpreventing dust from being scattered into the air from the robot.

For instance, conventional industrial robots for use under such cleanconditions are equipped with bellows-type covers 2 which surroundrespective articulates 1a which constitute dust sources, in order toprevent dust from being scattered into the ambient air.

This known dust prevention measures, however, involves problems in thatthe covers 2 acts as pumps upon expansion and contraction thereof todischarge dust together with air from the articulations through gapsbetween the covers 2 and the robot 1. In addition, the covers which arelarge in size disadvantageously increase the size of the robot as awhole. Moreover, a laborius work is required for demounting and mountingthe covers 2 before and after repair or maintenance.

DISCLOSURE OF THE INVENTION

The invention provides a compact size industrial robot which does notrequire a bellows type cover and which is easy to repair and maintain.It includes a plurality of arms, one or more articulation members orsliding articulation members each connected to each of said plurality ofarms, bearings for rotatably or slidably supporting said articulationmembers or said sliding articulation members, drive source means forrelatively rotating, swiveling or sliding said plurality of arms throughsaid articulation members or said sliding articulation members, the endof the arm attached to the tip end of said plurality of arms beingadapted to be positioned at any position in a space, internal air spacessubstantially closed by said arms, said articulation members, saidbearings or cover means or the combination thereof in a manner toseparate the rotating, sliding and contacting portions of said arms,said articulation members and said drive sources from the outside air,and negative pressure generating means for sucking air contained in theinternal air spaces to make the air pressure therein lower than that ofthe outside air. The latter serves to produce pressure gradients in thesmall clearances connecting the inside of the substantially closed robotto the outside thereof. This makes the air pressure inside of the robotlower than that of the outside air, and prevents dust in the robot frombeing scattered to the outside air.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a prior industrial robot having a meansfor preventing scattering of dust;

FIG. 2 is a fragmentary sectional view of an essential part of anindustrial robot of an embodiment of the invention having a means forpreventing scattering of dust;

10 FIG. 3 is a sectional view of an air passage taken along the lineA--A of FIG. 2;

FIG. 4 is a perspective view of the general constitution of anindustrial robot embodying the invention; and

FIG. 5 is a schematic view of a connection between substantially closedinternal air spaces of the industrial robot and a negative pressuregenerator.

THE BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment according to the invention will be described hereinbelowwith reference to FIGS. 2 to 5.

FIG. 2 shows an articulation of an industrial robot provided with a dustscattering prevention means in accordance with the invention. Areference numeral 3 denotes a stationary arm of the articulation arm,while 4 denotes a driven arm of the articulation. A numeral 5 designatesa main shaft 5. A servomotor 6 is fixed to the stationary arm 3 todrivingly rotate the main shaft 5 thereby driving the driven arm 4.Numerals 7 and 8 denote bearings through which the driven arm 4 isrotatably supported on the stationary arm 3. Numerals 9a and 9b denoteair passages provided in the stationary arm 3 and leading to a cavity 9cformed in the stationary arm 3, from the portions near the innerperipheries of the bearings 7, 8. The air passages 9a, 9b, the cavity 9cand internal air chamber 32a and 32b constitute an internal air space 9.Numerals 10a and 10b denote a reduction gear chamber accommodating areduction gear for reducing the speed of the servomotor 6. Numerals 10c,10d and 10e designate oil seals disposed between the portions 10a, 10bof the reduction gear chamber and the internal air space 9, while anumeral 10f denotes an oil seal provided in the other end of the portion10b of the reduction gear chamber. A numeral 11 denotes a pipe throughwhich air and dust are sucked from the cavity 9c in the stationary arm3, by the action of a negative pressure generator 12. A numeral 13denotes an air cleaner for removing the dust in the air sucked by thenegative pressure generator and discharging cleaned air.

Referring now to FIG. 3 which is a sectional view taken along the lineA--A in FIG. 2, the air passage 9a mentioned before is communicated withan area near the inner periphery of the bearing 8 through vent holes 9d,and also with the cavity 9c through a vent hole 9e.

FIG. 4 is a perspective view of an industrial robot embodying thepresent invention. A numeral 14 denotes a body of the robot, 15 a swivelarticulation, 16, 17 bending articulations, and 18, 19, 20 wristarticulations. The swivel articulation 15 is substantially closed by acover 21, and 22 denotes an upper arm and 23 a forearm. The internal airspaces of respective articulations are communicated with the negativepressure generator 12 through tubes 11a to 11d.

FIG. 5 shows the manner in which the substantially closed internal airspace of the articulations of the robot shown in FIG. 4 is communicatedwith the negative pressure generator.

There are shown four internal air spaces: namely, a first internal airspace 24 defined by the cover 21 covering the swivel articulation 15, asecond internal air space 25 defined in the bending articulate 16, athird internal air space 26 defined in the bending articulation 17 andthe upper arm 22, and a fourth internal air space 27 defined in thewrist articulations 18, 19, 20 and the forearm 23. A reference numeral28 denotes a flow rate regulator adapted for regulating the flow rate ofair sucked from the first internal air space, while 29, 30 and 31denote, respectively, pressure regulators for regulating the pressuresin the second, third and fourth internal air spaces 25, 26 and 27. Areference numeral 12a denotes a high/low pressure type negative pressuregenerator 12a, 13a an air cleaner 13a. 12b large-flow-rate type negativepressure generator 12b, and 13b and air cleaner 13b.

The operation of the thus constructed industrial robot is as follows.

During the operation pf the robot, dusts are generated from variousparts of the robot such as the meshing portions of the gears, bearings,oil seals, motor brushes and so forth. The dusts tend to be dischargedto the ambient air through the gaps in the bearings and covers. Thus,these gaps are materially regarded as being dust sources of the robot asa whole. With the arrangement shown in FIG. 2, the air in the internalair space 9 flows out through gaps associated with the bearings 7 and 8,so that these gaps constitute the material dust sources. Accordingly,dust can be prevented from being scattered if leakage of dust throughthese gaps are completely avoided. As a matter of fact, however, it isdifficult to keep these gaps completely airtight since these gaps areprovided in movable parts of the robot. In this regard, the air pressureabout the bearings 7 and 8 can be reduced relative to the pressure ofthe outside air by sucking the air in the air passages 9a and 9bprovided inside or the bearings 7 and 8 to another place, with theresult that air is caused to flow from outside of the bearings and tothe inside thereof, thereby preventing dust from being discharged to theoutside of the robot. In the embodiment described above, the airpassages 9a and 9b are communicated with the cavity 9c, from which airis discharged through the pipe 11 by means of the negative pressuregenerator 12. With such arrangement, the air pressure in the cavity 9ccan be prevented from being increased in spite of the temperature riseof the servomotor 6 and can normally be rendered negative relative tothe pressure of the ambient air, thereby enabling preventing leakage ofdust through small gaps between the parts of the robot. The airdischarged from the negative pressure generator 12 is discharged to theenvironment after it is relieved of dust by means of the air cleaner 13.

The reduction gear chamber 10a and 10b is oil-lubricated and is madeliquid tight by the oil seals 10c, 10d, 10e and 10f to eliminate leakageof the lubricating oil to the outside. If the vapor of the lubricatingoil should leak outside through the oil seals 10c, 10d or 10e, it wouldnot be scattered to the environment since it is discharged from theinternal air space 9 through the pipe 11 by means of the negativepressure generator 12. In addition, the area on the side of the oil seal10f is completely closed by the driven arm 4 to be adequately separatedfrom the outside air.

The fundamental effects described above can be applied to the case of anindustrial robot shown in FIG. 4 which has multiple degrees of freedomand a plurality of internal air spaces as shown in FIG. 5. The operationin the embodiment shown in FIG. 5 will be described hereinbelow. Therobot has four internal air spaces, of which second, third and forthinternal air spaces contain bearings as dust sources, as in the case ofthe embodiment shown in FIG. 2. These bearings are of a sealed type andareas of clearances therein are small. On the one hand, these bearingsare located near a work handled by the robot, so that they need be ofhighly dust-free characteristics. In this regard, a vacuum pump is usedin a negative pressure generator 12a and pressure gradients about therespective bearings are adjustably balanced by means of pressureregulators 29, 30 and 31 to attain high dust-free characteristics. Thefirst internal air space 24 is surrounded primarily by a cover 21 whichpresents a relatively large gap area. To compensate for this, an exhaustfan having a large capacity is used in the negative pressure generator12b and a flow rate of discharge is adjusted by a flow regulator 28 toprevent scattering of dust.

In the above embodiments, the invention has been described with respectto an industrial robot having articulations which are adapted to swivelor pivot relative to one another. The invention, however, is not limitedto such type of industrial robot but can be applied to an industrialrobot of the type having sliding articulations which permit a pluralityof arms to linearly move to one another.

INDUSTRIAL APPLICABILITY

As apparent from the foregoing description, the invention provides thefollowing advantages.

(1) The interior of the robot body is made closed separately from theambient air and negative pressure is produced in the internal airspaces, so that dust generated during the operation of the robot isprevented to embody a dust-free industrial robot of high quality.

(2) The robot body is made compact and is easy for maintenance andinspection.

(3) Even when operations are conducted in a decompression room or plenumroom, the pressure in the internal air spaces within the robot body ismade negative relative to the room pressure to readily embody adust-free industrial robot of a high performance.

(4) The bearings need not be of an oil free type, and so it is possibleto provide an industrial robot which is inexpensive, reliable anddurable.

What is claimed is:
 1. In an industrial robot including a stationary armand a driven arm for constituting articulations, bearing means forrotatably supporting said driven arm relative to said stationary arm,and a driven source provided in said stationary arm for swiveling saiddriven arm relative to said stationary arm, the tip end of said drivenarm being adapted to be positioned at any position in a space, theimprovement comprising an internal air chamber formed by substantiallyclosing a space surrounded by said stationary arm, said driven arm andsaid bearing means in a manner to separate the same from the outsideair; and air passage provided in a wall of said stationary arm, said airpassage being in communication with an area of said internal air chambernear an inner peripheral side of said bearing means and connecting saidinternal air chamber to a cavity provided within aid stationary arm;negative pressure generating means for sucking air contained in saidcavity, said air passage and said internal air chamber to make the airpressure therein lower than the pressure of the outside air; and pipingmeans for connecting said negative pressure generating means to saidcavity.
 2. An industrial robot as set forth in claim 1, furthercomprising an air cleaner communicated to the suction side of saidnegative pressure generating means.
 3. An industrial robot as set forthin claim 1, wherein said negative pressure generating means comprises avacuum pump.
 4. An industrial robot as set forth in claim 1, whereinsaid negative pressure generating means comprises an exhaust fan.
 5. Anindustrial robot, comprising(a) a stationary arm and a driven arm, (b)bearing means for relatively and rotatably supporting said stationaryarm and said driven arm, (c) a gear box means provided between saidstationary arm and said driven arm for containing therein reductiongears which serve to drive said driven arm relative to said stationaryarm, (d) motor means for driving the gears within said gear box, (e)said bearing means, said driven arm and said stationary arm defining asubstantially closed internal air chamber to separate said internal airchamber from the outside air, (f) air passage means formed within a wallof said stationary arm and opened to said internal air chamber, and (g)negative pressure generating means for communicating with said airpassage means for making air pressure in said internal air chamber lowerthan outside air pressure.
 6. An industrial robot as set forth in claim5, further comprising an air cleaner communicated to the suction side ofsaid negative pressure generating means.
 7. An industrial robot as setforth in claim 5, wherein said negative pressure generating meanscomprises a vacuum pump.
 8. An industrial robot as set forth in claim 5,wherein said negative pressure generating means comprises an exhaustfan.
 9. In an industrial robot including a stationary arm; a driven arm;bearing means for rotatably connecting said stationary arm and saiddriven arm relative to each other; and gear box means disposed betweensaid stationary arm and said driven arm and including (i) reduction gearmeans for drivingly rotating said stationary arm and said driven armrelative to one another and (ii) sealing means for sealing an interiorspace defined by said gear box means; the improvement wherein one ofsaid stationary arm and said driven arm is at least partially enclosedwithin a space defined by the other of said stationary arm and saiddriven arm; said sealing means, said bearing means, said stationary armand said driven arm defining an internal chamber; said stationary armincluding a wall having an internal air passage in communication withsaid internal chamber, said air passage being adapted to be connected toa negative pressure generating means for maintaining said internalchamber at a negative pressure upon actuation of said negative pressuregenerating means.
 10. An industrial robot as set forth in claim 9,further comprising an air cleaner communicated to the suction side ofsaid negative pressure generating means.
 11. An industrial robot as setforth in claim 9, wherein said negative pressure generating meanscomprises a vacuum pump.